Ascorbate (AsA), an essential antioxidant for both plants and the human body, plays a vital role in maintaining proper functionality. Light plays an important role in metabolism of AsA in horticultural plants. Our previous research has revealed that subjecting lettuce to high light irradiation (HLI) (500 μmol·m⁻²·s⁻¹) at the end-of-production (EOP) stage effectively enhances AsA levels, while the optimal light quality for AsA accumulation is still unknown. In this study, four combinations of red (R) and blue (B) light spectra with the ratio of 1:1 (1R1B), 2:1 (2R1B), 3:1 (3R1B), and 4:1 (4R1B) were applied to investigate the biosynthesis and recycling of AsA in lettuce. The results demonstrated that the AsA/total-AsA content in lettuce leaves was notably augmented upon exposure to 1R1B and 2R1B. Interestingly, AsA levels across all treatments increased rapidly at the early stage (2–8 h) of irradiation, while they increased slowly at the late stage (8–16 h). The activity of L-galactono-1,4-lactone dehydrogenase was augmented under 1R1B treatment, which is pivotal to AsA production. Additionally, the activities of enzymes key to AsA cycling were enhanced by 1R1B and 2R1B treatments, including ascorbate peroxidase, dehydroascorbate reductase, and monodehydroascorbate reductase. Notably, hydrogen peroxide and malondialdehyde accumulation increased dramatically following 16 h of 1R1B and 2R1B treatments. In addition, although soluble sugar and starch contents were enhanced by EOP-HLI, this effect was comparatively subdued under the 1R1B treatment. Overall, these results indicated that AsA accumulation was improved by irradiation with a blue light proportion of over 50% in lettuce, aligning with the heightened activities of key enzymes responsible for AsA synthesis, as well as the accrual of hydrogen peroxide. The effective strategy holds the potential to enhance the nutritional quality of lettuce while bolstering its antioxidant defenses.

Early flowering is a key element of the rice speed-breeding protocol that enables improved genetic gain and accelerates the cultivation of new varieties. Although far-red light (FR) is commonly used to modulate plant developmental processes, the mechanisms by which it influences flowering and growth in rice are poorly understood. In this study, the control treatment (CK) consisted of red-blue-green composite light at 300 μmol m⁻² s⁻¹, while two additional treatments were applied: one with the photon flux density (PFD) increased to 350 μmol m⁻² s⁻¹ (HI—high intensity) under the same light spectrum as CK, and the other supplemented with 50 μmol m⁻² s⁻¹ of FR based on CK. The results demonstrated that both elevated PFD and supplemental FR significantly enhanced vegetative growth, as evidenced by increased plant height, tiller number, leaf area, and biomass accumulation, along with improved photosynthetic capacity and chlorophyll fluorescence. Under the FR treatment, flowering occurred 53 days after transplanting, which was 12 days and 9 days earlier than in the CK and HI treatments, respectively. Physiological profiling revealed that FR enrichment significantly increased leaf soluble sugar and starch levels, while simultaneously decreasing chlorophyll and carotenoid concentrations. FR also reshaped the endogenous hormonal profile, which was marked by elevated levels of gibberellin (GA3) and abscisic acid (ABA), and reduced auxin (IAA) content. Transcriptomic profiling revealed that FR enrichment activated the circadian rhythm pathway and upregulated genes associated with photoperiodic flowering and inflorescence development. In summary, FR promotes rice growth and early flowering through the integrated regulation of leaf area expansion, enhanced photosynthetic efficiency, hormonal rebalancing, and activation of flowering gene expression. This study provides a theoretical foundation and technical support for optimizing light environments and improving the economic viability of crop speed breeding systems in controlled environmental facilities.

Rice is central to global food security, and plant factories enable precise control of lighting conditions. However, genotype-specific responses to supplemental blue light across the full crop cycle remain poorly understood. Here, Nipponbare and CP511 were grown from transplanting to maturity under a green, red, and far-red background supplemented with 0, 50, 100, 150, or 300 μmol m⁻² s⁻¹ blue light (B0–B300). In both genotypes, increasing supplementation reduced plant height, increased tillering and biomass, advanced flowering by 9–13 d, and enhanced pigment content and photosynthetic capacity. Nipponbare maintained photosynthetic improvements at higher supplementation levels, whereas CP511 plateaued earlier. In Nipponbare, grain yield increased from 1.46 g plant⁻¹ at B0 to 5.09 g plant⁻¹ at B100 but did not increase significantly thereafter, despite enhanced photosynthesis and sucrose metabolism. At B300, seed setting declined to 54%, with reduced dry-matter allocation to panicles. In CP511, higher supplementation increased total panicle production but not effective panicle formation, seed setting, or grain yield, which changed from 3.29 g plant⁻¹ at B150 to 2.49 g plant⁻¹ at B300. Thus, the most favorable treatment depended on coordination between source capacity and effective reproductive sink formation rather than maximal photosynthesis or panicle production alone.